[5] The Cassel Report investigated 76 killings attributed to the group and found evidence that UDR soldiers and RUC police officers were involved in 74 of those.

[14] By the mid-1970s the violent ethno-political conflict known as the Troubles had radically transformed the daily lives of people in Northern Ireland; after five years of turbulent civil unrest, the bombings and shootings showed no signs of abating.

Fully opposed to the agreement, the UVF and UDA/UFF wanted no part of the truce, while British military commanders resented being told to stop their operations against the IRA just when—they claimed—they had the Provisionals on the run.

Ulster loyalist paramilitaries, fearing they were about to be forsaken by the British government and forced into a united Ireland,[17] increased their attacks on Roman Catholic civilians and nationalists.

Increased Loyalist attacks were partially due to their discovery that MI6 agent Michael Oatley had engaged in negotiations with a member of the IRA Army Council during which "structures of disengagement" from Ireland were discussed.

[19] It was during this exceptionally violent period that a group of loyalist extremists formed a loose alliance that in 2003 was belatedly given the name "Glenanne gang".

[6] The gang, which contained over 40 known members, included soldiers of the British Army's Ulster Defence Regiment (UDR), active police officers within the RUC and its Special Branch, covert agents from the Secret Intelligence Service (SIS), more commonly known as MI6 (i.e. Military Intelligence, Section 6), and extremists from both the nominally illegal Mid-Ulster Brigade as well as the state sanctioned Ulster Defence Association (UDA).

[70] In 2004, the Pat Finucane Centre asked Professor Douglas Cassel (formerly of Northwestern University School of Law in Chicago) to convene an international inquiry to investigate collusion by members of the British security forces in sectarian killings in Northern Ireland committed during the mid-1970s.

The interviews revealed many similarities in the way the attacks were carried out, while various documents (including the Barron Report) established a chain of ballistic history linking weapons and killings to the gang.

[72]The Glenanne gang has been linked to the following attacks and/or incidents:[4][73] According to the Barron Report, Billy Hanna had asked James Mitchell for permission to use his farm as a UVF arms dump and bomb-making site.

[118] According to submissions received by Mr Justice Barron, the Glenanne farm was used to build and store the bombs that exploded in Dublin and Monaghan.

The report states they were placed onto Robin Jackson's poultry lorry, driven across the border to a carpark, then activated by Hanna and transferred to three allocated cars.

[119] Weir also stated that on one occasion an RUC constable gave him two weapons to store at the Glenanne farm: He then offered me the two sub-machine guns because he knew about my connection to Loyalist paramilitaries.

There were no casualties, however, as Mitchell's floor plans had been inaccurate, and the customers had fled into the pub's living quarters for safety once the shooting had commenced outside, and the bomb only caused structural damage to the building.

[42] Mr. Justice Barron concluded in his report: It is likely that the farm of James Mitchell at Glenanne played a significant part in the preparation for the attacks [Dublin and Monaghan bombings].

[121] In May 2024 Iain Livingstone, head of Operation Denton, said that there was no doubt of collusion between the Glenanne gang and British authorities in the Dublin and Monaghan bombings.

[122] On 31 July 1975, four days after Hanna's shooting and Jackson's assumption of leadership of the Mid-Ulster brigade,[123] the Miami Showband's minibus was flagged-down outside Newry by armed UVF men wearing British Army uniforms at a bogus military checkpoint.

Two UVF men (Harris Boyle and Wesley Somerville) loaded a time delay bomb on the minibus but it exploded prematurely and killed them.

[124] The remaining UVF gunmen then opened fire on the bandmembers, killing three (Brian McCoy, Anthony Geraghty and Fran O'Toole) and wounding two (Stephen Travers and Des McAlea).

[130] Miami Showband survivors Stephen Travers and Des McAlea both testified in court that a man with a "crisp, clipped English accent, and wearing a different uniform and beret" had been at the scene of the explosion and subsequent shootings.

[131] The Cassel Report concluded that there was "credible evidence that the principal perpetrator [of the Miami Showband attack] was a man who was not prosecuted – alleged RUC Special Branch agent Robin Jackson".

[133] The co-ordinated sectarian shootings of the Reavey and O'Dowd families, allegedly perpetrated by the Glenanne gang and organised by Robin Jackson, was followed the next day by the Kingsmill massacre.

The "South Armagh Republican Action Force" claimed responsibility, saying that the shooting was retaliation for a string of attacks on Catholic civilians in the area by loyalists, particularly the Reavey and O'Dowd killings.

[136][137] The attack was allegedly called off because the UVF leadership ruled it would be "morally unacceptable" and would lead to a harsh IRA response and likely civil war.

In November 2017 Mr Justice Treacy gave further judgement, confirming that he would be issuing an order of mandamus that would require compliance by the Chief Constable and the PSNI.

[151][152][153] In July 2019 the Court of Appeal ruled that a full, independent inquiry into allegations of collusion between security services and the Glenanne gang should be held.